1. Field of the Invention
The present invention relates generally to the field of telecommunications, and more particularly to improvements in the way in which DTMF tones may be used to control diverse systems such as telephony-based systems.
2. Description of the Related Art
There exists an increasing number of advanced voice applications such as voice mail, telephone banking systems and such like, which are controllable by a user through a telephone handset. Although voice recognition technology is now at a level that may now enable users to control such applications using spoken commands, the majority of such systems still rely on control signals in the form of DTMF tones generated by telephone handsets.
Typically a voice application is accessed through a telephone-type connection, for example by dialing a subscriber number associated with the application. Once connected, the user is typically presented with spoken menus that may be navigated through by sending DTMF tones from the user handset to the application. When finished with the application, the user typically hangs-up and is subsequently ready to place or receive new calls in a conventional manner.
Whilst accessing such advanced applications in the above-described manner is generally problem free, problems may arise when accessing such applications via intermediate services such as third party network operators, for example using a telephone calling card, or ‘dial-out’ conferencing services.
In the case of telephone calling cards a user typically places a free or low-cost call to a call center which, upon connection, the user enters authorization information such as an account number in order to gain access to their account. Typically the authorization information is entered by sending DTMF tones from the user's telephone handset to the call center. Once authorization is complete a dial tone is generally obtained allowing the user to enter, again using DTMF tones, a new subscriber number to which to be connected. In addition to being responsive to DTMF tones to allow a new call to be place, the call centers typically allow the user to hang-up a call without physically terminating the connection between the user and the call center by sending a predetermined DTMF tone or tone sequence—this allows a user to make multiple calls one after the other without having to redial the call center and reenter the authorization information each time. The call center may also respond to other DTMF tones to inform the user, for example, of credit remaining, account expiry date etc.
If such an intermediate service is used to access a voice application a situation may arise in which both the intermediate service and the voice application are responsive to DTMF tones sent from a user handset. If the DTMF tones, for example, intended for a voice mail application are interpreted by the call center the results may be at best unpredictable and in any case are likely to result in confusion for the user. This problem is further exacerbated by the fact that the vast majority of telephone handsets can only generate 12 different DTMF tones; a fact which increases the probability that different DTMF controllable applications will be responsive to at least some common DTMF tones.